1. Field of the Invention
The present invention relates to a cooling technique of a power semiconductor device.
2. Description of the Background Art
In order to dissipate heat generated from a power semiconductor element to the exterior, a conventional power semiconductor device has a copper plate bonded to a back surface of the power semiconductor element with a brazing material and a ceramic plate bonded to the copper plate with a brazing material provided therein, a back surface of the ceramic plate being in contact with an external cooling system (a cooling plate having a path for passing a refrigerant liquid formed therein) through adhesion grease. The conventional power semiconductor device is disclosed in Japanese Patent Application Laid-Open Nos. 2002-270748, 2002-093974 and 2001-332679.
In the conventional semiconductor device, members for the copper plate and the ceramic plate need to be used to attach the cooling system to the semiconductor device, and grease needs to be coated at the time of the attachment to ensure a contact surface and reduce contact thermal resistance. This sort of structure has been an obstacle in seeking size reduction of the device while further increasing the cooling efficiency to heat generated from the power semiconductor element.